This core is to establish a facility to carry out laboratory investigations on oxygen free radical damage for the Seattle Gastrointestinal Program Project. Our goal is to ascertain whether damage or mutations resulting from oxygen free radicals accumulate in pre- cancerous tissues or in tumors. The quantitation of oxygen free radial damage to DNA will be carried out by measuring the content of 8-oxo- deoxyguanosine and 5-hydroxycytidine in DNA from cells obtained from pancreatic cancer, ulcerative colitis, and colon cancer. 8-oxo- deoxyguanosine is a well documented marker of oxygen free radical damage to DNA. We have presented evidence that 5-OH-deoxycytidine is produced by oxygen free radicals and is highly mutagenic. Both of these adducts will be quantitated by high pressure liquid chromatography coupled with electrochemical detection. The quantitation of mutations due to oxygen free radical damage to DNA will be established by measuring the frequency of CC>TT mutations in a target gene, DNA polymerase-beta in cells obtained in each of the projects in this Program; the CC>TT mutations can be diagnostic of oxygen free radical damage to DNA and can be quantitated at a frequency of 10/-6 by a new PCR based mismatched assay. Together these studies on oxygen free radical damage and mutations provide a spectrum of probes to analyze the contribution of oxygen free radical damage to these important cancers.